The present invention relates to a heat-pump hot water supply apparatus.
In general, a heat-pump water heater or hot water supply apparatus of the conventional art is of a hot-water storage type, having a large-size hot-water storage therewith, from 300 L to 500 L of in the capacity thereof, in the similar manner to an electric water heater or hot-water supplier, wherein hot water stored is supplied for use during the day-time, while boiling the water by means of a heat pump circuit during the nighttime with using discounted cheap electricity, which is cheap in the night, to be stored in the storage tank.
In recent years, a heat-pump water heater or hot water supply of an instantaneous heating type is proposed, finally, in which the water is heated, directly, to be supplied through a heat-pump operation, every time when using the hot water.
Such the heat-pump water heater of an instantaneous heating type, disclosed in the following Patent Document 1, for example, has no storage tank therein, so as to build up a main body of the water heater and a main body of the heat pump as a unit, and thereby obtaining a light weight, and space saving of an area where the it is installed.
Patent Document 1: Japanese Patent Laying-Open No. 2003-240344 (2003)
With the heat-pump water heater of an instantaneous heating type, being disclosed in the Patent Document 1, there is still remained a problem unsolved, in the rise-up characteristics or property thereof, i.e., it takes a long time to start up heating just after the operation thereof, being an important problem for the heat-pump hot water supply apparatus of an instantaneous heating type.
For achieving such instantaneous heating type heat-pump water heater, it is important to stabilize the starting characteristics or property, since the heating operation must be conducted, intermittently, every time when supplying the hot water. In particular, when it is stopped in the winter season, a large amount of refrigerant resides within an evaporator in the form of liquid. And, just after starting of the operation, the liquid refrigerant flows out, suddenly, into a compressor, so that it obstructs the starting operation; therefore, it is necessary to work out a countermeasure for such phenomenon, i.e., so-called a sleep in low-temperature (hereinafter, low-temperature sleep) condition. However, no measure is disclosed for dissolving such the problems, in the instantaneous heating type heat-pump water heater shown in the Patent Document 1.
Thus, with the instantaneous heating type heat-pump water heater of the Patent Document 1, the refrigerant is liquefied within the evaporator, radiating heat thereof, during stoppage of the compressor; however, it takes a time from 5 to 6 minutes from the time when a cock of water service is opened up to the time when a hot water of proper temperature (about 42° C.) comes out therefrom, in the winter season, i.e., so as to heat that liquefied refrigerant into a condition for heating the water by the heat-pump circuit. Also, there is provided no countermeasure for improving the characteristics of the low-temperature sleep mentioned above;
therefore, it is very difficult to put the heat-pump water heater into a practical use thereof.